The present application is based on and claims priority to Japanese Patent Application No. 2000-359493, filed Nov. 27, 2000, which is hereby expressly incorporated by reference.
1. Field of the Invention
This invention relates to an outboard motor, and more particularly to an improved fuel supply system for an outboard motor.
2. Description of the Related Art
A typical outboard motor comprises a power head and a housing depending from the power head. The power head includes an internal combustion engine that drives a marine propulsion device (e.g., a propeller) through a driveshaft and a propulsion shaft, which are both journaled within the housing. The marine propulsion device is attached to the end of a propulsion unit, which extends from housing and is in a submerged position. The internal combustion engine is typically covered by a protective cowling. The protective cowling typically comprises an upper portion and lower portion, which are removably mounted to each other by hooks or other coupling mechanisms, such as, for example, hooks.
There is an increasing emphasis on obtaining more effective emission control, better fuel economy and, at the same time, continued high or higher power output in outboard motors. Accordingly, four-cycle engines have started to replace two-cycle engines in outboard motors. In a similar manner, it has been suggested that direct fuel injection be used in outboard motors to further reduce emissions and improve performance.
A typical fuel injection system includes a fuel tank, a low-pressure fuel pump, a high pressure fuel pump, a plurality of fuel injectors and an injection control device. The low pressure fuel pump delivers fuel from the fuel tank to the fuel vapor separator through a first delivery passage. The high pressure fuel pump, in turn, transfers the fuel from the vapor separator to the fuel injectors. The fuel injectors are arranged to spray fuel directly into the combustion chamber of the engine, under the control of the injection control device. Excess fuel is returned to the vapor separator through a return passage.
It is well known that fuel vapors can collect in the fuel injection system. Their concentration in the fuel-supply system can vary with operating and environmental conditions. This can cause the fuel injectors to unpredictably run lean or rich, resulting in poor engine performance. The vapor separator removes the fuel vapors from the liquid fuel such that the fuel vapors are not mixed with the liquid fuel and injected into the combustion chamber. A vent is provided on the vapor separator to remove the fuel vapors from the separator. Venting the fuel vapors directly to the atmosphere is generally not an acceptable solution because of environmental concerns; as such, the fuel vapors typically are mixed in with an incoming air charge. This does not completely eliminate the unpredictability associated with fuel vapors because the fuel vapors in the intake charge can still affect the fuel/air ratio.
Four cycle engines tend to produce higher exhaust temperatures as compared to two-cycle engines. As such, the temperature within the cowling of a four-cycle outboard motor tends to be higher as compared to a two-cycle outboard motor. This increase in temperature can result in an increased amount of fuel vapors in the fuel system. A need therefor exists for reducing the amount of fuel vapors in a four-cycle outboard motor.
Accordingly, one aspect of the present invention is a four-cycle engine for powering an outboard motor. The engine comprises a plurality of combustion chambers arranged generally vertically above one another. The combustion chambers are formed by at least an engine body, a cylinder head assembly and a piston that moves relative to the engine body and the cylinder head assembly. A crankshaft extends in a generally vertical direction and is coupled to the piston such that movement of the piston causes the crankshaft to rotate. At least one air intake port and at least one exhaust port communicate with the combustion chamber. An intake valve is moveable between an open and closed position and an exhaust valve is moveable between an open and closed position. A valve actuating mechanism actuates the exhaust and intake valves. A head cover assembly covers the valve actuating mechanism. A fuel injection system comprises at least one fuel injector, a fuel pump that communicates with at least one of the fuel injectors, a vapor separator that communicates with the fuel pump through at least a first supply line, and at least one return line that is arranged to return fuel to the vapor separator from a point downstream of the fuel pump. The vapor separator includes a vent and a fuel absorption canister that includes a fuel absorption media. The canister being located in the vapor separator below the vent.
Another aspect of the present invention is a four-cycle engine for powering an outboard motor. The engine comprises a plurality of combustion chambers arranged generally vertically above one another. The combustion chambers are formed by at least an engine body, a cylinder head assembly and a piston that moves relative to the engine body and the cylinder head assembly. A crankshaft extends in a generally vertical direction and is coupled to the piston such that movement of the piston causes the crankshaft to rotate. At least one air intake port and at least one exhaust port communicate with the combustion chamber. An intake valve is moveable between an open and closed position and an exhaust valve is moveable between an open and closed position. A valve actuating mechanism actuates the exhaust and intake valves. A head cover assembly covers the valve actuating mechanism. A fuel injection system comprises at least one fuel injector, a fuel pump that communicates with at least one of the fuel injectors, a vapor separator that communicates with the fuel pump through at least a first supply line, and at least one return line that is arranged to return fuel to the vapor separator from a point downstream of the fuel pump. The vapor separator including a vent and means for reducing an amount of hydrocarbons entering the vent.
Yet another aspect of the present invention is a vapor separator for an internal combustion engine. The vapor separator comprises a housing, which defines a cavity, a first inlet conduit that is connected to a first fuel supply line, a first outlet conduit that is connected to a second fuel supply line, and a second inlet conduit that is connected to a fuel return line, and a vent. The vapor separator is arranged such that liquid fuel is collected in a lower portion of the vapor separator and vapors are collected in an upper portion of the vapor separator. The first and the second inlet conduits have outlets located in the lower portion. The first outlet conduit has an inlet also located in the lower portion. The vent has an inlet located in the upper portion. The vapor separator further includes a fuel absorption canister that includes a fuel absorption media. The canister is located in the vapor separator below the inlet of the vent and above the outlets of the first and second inlet conduits and the inlet of the first outlet conduit.
Still yet another aspect of the present invention is a vapor separator for an internal combustion engine. The vapor separator comprises a housing, which defines a cavity, a first inlet conduit that is connected to a first fuel supply line, a first outlet conduit that is connected to a second fuel supply line, and a second inlet conduit that is connected to a fuel return line, and a vent. The vapor separator is arranged such that liquid fuel is collected in a lower portion of the vapor separator and vapors are collected in an upper portion of the vapor separator. The first and the second inlet conduits have outlets located in the lower portion. The first outlet conduit has an inlet also located in the lower portion. The vent has an inlet located in the upper portion. The vapor separator further includes means for reducing an amount of hydrocarbons from entering the inlet of the vent.